Fracking, the popular abbreviation for hydraulic fracturing, is a technique which injects highly-pressurized fluid into a well to split the rock and allow access to natural gas trapped within.
Energy companies, driven in no small part by dwindling reserves of easy-to-access fossil fuels, are increasingly turning to so-called unconventional sources of fossil fuels. Shale gas is one of these; and hydraulic fracturing promises to open up access to what is claimed to be vast to sources of natural gas, and profits. National governments too, driven by a desire for greater energy independence, want access to these reserves of natural gas.
But big questions remain about the environmental safety of fracking: Will fracking cause more earthquakes? Will the chemicals used contaminate drinking water? What will be the impact on small farms? Does natural gas obtained by fracking have similar greenhouse gas emissions to other natural gas?
Energy companies downplay all of these concerns. Politicians focus on energy independence. Environmentalists urge caution. Whatever side you're on, fracking is likely to remain an issue in the forefront of energy policy for some time.